1. How did (1) complexity and (2) human factors play a role in the train wrecks discussed in the videos? Your answer must include specific references to events, items or issues discussed in the videos. Discuss at least one feature developed for modern railroad systems which has been developed to improve reliability/avoid failure. (at least 300 words)
Following the Pickle Wreck, investigation found that a missing cotter pin for to retain a component of the switch. It was then speculated that the lack of a cotter pin resulted in the crash because it was essential in keeping the switch position held. This change of direction caused the train to crash when the speeding train's vibrations cause the switch to swap directions after initially being changed. This is likely why the first engine passed the switch but subsequent cars crashed as the first engine's vibrations cause the unsecure switch to change in the direction of the pickle factory. It was speculated that maintenance personnel had failed to replace the cotter pin following maintenance. [7] Additionally, the switch had complex mechanisms with many parts moving relative to another. More moving parts introduces more failure modes. In modern switches the mechanical nature of these switches and be simplified to use less moving parts by using electrical components.
Other modern measures include automated-braking technologies which can automatically brake a train if abnormal conditions are detected. This system is called Positive Train Control. The Positive Train control system or PTC uses a GPS or global positioning system to measure speed as well as position from certain breaking limit positions; such limits are set such that the train can brake and lose enough speed prior to entering a turn for example [9]. The PTC system can also detect the positions of trains relative to each other and brake trains that are on a collision course. The PTC is coupled with warning alarms for the locomotive engineering, providing "advance warning of movement authority limits, speed limits and track conditions ahead, giving the engineer time to react and bring the train to a safe speed or controlled stop." [9] However, human factors are still relevant. The PTC system cannot prevent accidents due to poor maintenance, and illegal entry onto the track of unauthorized people or vehicles. This goes to highlight that even with the most advanced technology with automated systems, human factors are still a source of failure.
2. Explain how complexity of engineered systems and the stress placed on a system by extreme conditions (like a hurricane, tsunami or earthquake) can be an especially dangerous combination. Give a detailed example of how these two factors have a synergistic effect in causing disaster. Also, cite any evidence you find for any "normalization of deviance" in your example. (at least 300 words)
The complexity of engineered systems may result in undiscovered vulnerabilities that can be exploited by extreme conditions such as natural disasters. In the case of New Orleans' Hurricane Protection System, a bureaucratic mess as well as a complex engineering project resulted in a complex mess. This resulted in various vulnerabilities due to piecemeal construction and design failures. When an extreme condition struck, the system then failed.
A complex system also means estimations must be made. In the case of the failure of the 17th Street Canal levee, the soil strength was overestimated due to "nonconservative interpretation of sample data and a low factor of safety". [4] Estimations are often necessary because it may not always be feasible to build an onsite prototype to get a true test of strength. Thus, engineers must rely often on a limited set of data and interpolate. However, because of this limitation, engineers must use larger factor of safeties to avoid underdesigning. However, overdesigning is also not without risks. Overdesigning would result in higher costs and would do nothing but exacerbate the already messy situation. High costs resulted in the Hurricane Protection being built in piecemeal resulting in poor links between adjacent structures. This weak link failed during extreme conditions.
This piecemeal structure of the Hurricane Protection System resulted in a system that "was a system in name only". [5] In the 40-year effort of the Hurricane Protection System, this piecemeal construction became accepted as normal. This is an example of the "normalization of deviance". Over the many years of this project, the normalization resulted in compounding faults and weaknesses. Poor structures were built on poor soil next to, in piecemeal, a differently designed structured. Flaws were hastily patched in rough manner rather than being rebuilt from scratch.
Poor engineering was also a factor because the design of these protection systems were not rigorously reviewed by experts. Because of the scale of the failure, it can be said that it wasn't simply one system element that failed but many. This suggests that poor decisions were made many times throughout the years of the project.
In other words, while the disaster at New Orleans was the result of a brief disaster, it was compounded by the normalization of poor human factors and design over a long period.
3. Suggest how an engineered system (like a transportation system, an energy generation and distribution grid, or a coastal city's infrastructure) can be designed to survive a natural disaster (taking into account the risks inherent in complexity). Cite references in your answer – you should use at least 2 or 3 references to real systems designed or under development and specifically show how the designers took past disasters into account. (at least 450 words)
One danger during a natural disaster such as an earthquake is injury due to damaged structure. For example, a severe earthquake may result in the collapse of underground subway stations and tunnels. Such collapses can trap trains and passengers and when underground, exit paths are limited to a few exits and entrances. The first line of defense, then, are early warning systems based on a network of sensors and instruments that detect preliminary waves originating from an earthquake's epicenter. Such systems can offer mere seconds of warning but this may be sufficient because they may give time to "slow or stop trains, get out of a dangerous location, and prepare for shaking". [1] San Francisco's BART is leading the way in beta testing such systems given California's prime earthquake location. In Japan, the rail system uses a nationwide system of seismometers and public alert systems which is a more advanced implementation of the aforementioned technology. Such technology saved many lives during the 2011 Japanese earthquake because when the waves of the 9.0 magnitude earthquake were detected, the high speed trains were immediately braked from 200 mph which resulted in no derailments or injuries. [1] Further, modern Japanese high speed rail trains are equipped with safety devices that prevent derailment especially when the train is very close to the epicenter of the earthquakes and therefore not able to be stopped prior to being hit by the earthquake waves.
An example of a natural disaster resilient power grid would be a more localized system known as a microgrid. Despite a massive wildfire, the rooms at the Jackson Racheria Resort remained powered while many other nearby areas were left powerless as infrastructure was burnt to the ground. The resort was subsequently turned into an a refuge for many, now left homeless and powerless. The resort remained powered because of its "network of generators and electrical equipment that gave the rancheria temporary energy independence from the regional power grid". [4] Because most people rely on a distant powerplant to produce their power, if the powerlines connecting them and this plant are damaged, they may lose power. In this case, the transmission of power is the weak link. By bringing the production of power closer to oneself, such localized power systems can be rapidly utilized to provide reliable power following power loss from the main source. This can be supplement by renewable resources such as solar power which requires no external human provided resources for power. On the other hand, because such renewable resources are by their nature required to be outdoors, they are also more susceptible to the elements. So to be reliable during natural disaster, they must also be resilient. Because natural disasters can occur anywhere, it is beneficial to invest, whether privately of publicly in such microgrid systems. Be sure to include a brief reflection at the end of the assignment which addresses (a) what you learned -- especially something new or unusual - from the assignments, and (b) how it builds on the other lessons and assignments in the course.
Source:
[1] https://howwegettonext.com/waiting-for-a-natural-disaster-c3f11e0f6783
[2] https://thesource.metro.net/2012/08/10/designing-a-subway-to-withstand-an-earthquake/
[3] http://www.govtech.com/dc/articles/Microgrids-Sustain-Power-During-Natural-Disasters.html
[4] https://www.asce.org/question-of-ethics-articles/july-2015/
[5] http://articles.latimes.com/2006/jun/02/nation/na-levee2
[7] http://www.trainsarefun.com/lirr/lirrwrecks/lirrwrecks.htm
[8] https://www.nytimes.com/2017/12/20/us/amtrak-train-safety.html